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United States Department of Agriculture

Agricultural Research Service

Title: Cyclin B1 Transcript Levels During the Transition from Maternal to Zygotic Control of Development in Porcine Embryos

item Matteri, Robert

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 12, 1998
Publication Date: N/A

Technical Abstract: The 4-cell stage of early porcine embryonic development has been considered the time of maternal to zygotic transcript transition (MZTT). This study evaluates the timing of the MZTT within the 4-cell stage porcine embryo in regard to cyclin B1, a G2 to M cell cycle transition participant. Two-cell embryos were recovered and cultured in vitro. Embryos were allowed to develop until different time points (5, 10, 18, 25, or 33 hr post 4-cell cleavage (P4cc)), representing early, mid, and late periods within the 4-cell stage. Poly-A mRNA was isolated from each individual embryo (n=5 embryos/time). Following RT, cPCR was used to co-amplify both an embryonic derived 503 bp cyclin B1 cDNA along with an exogenous 435 bp truncated competitor DNA. In addition, a separate cPCR using serial dilutions of 503 bp cyclin B1 cDNA along with competitor was used to generate a standard curve. PCR products were separated out on agarose gels sand Southern blotted. A relative mRNA value for each embryo was generated by forming a ratio of cyclin B1 cDNA:competitor, and relating this value to the standard curve. The mean values (attomole/embryo) and standard errors for the 5, 10, 18, 25 and 33 hr time points were 26.4 +/ 5.6**a, 18.7 +/ 4.1**ab, 19.8 +/ 5.1**ab, 11.8 +/ 1.2**bc, and 5.0 +/ 0.5**c, respectively (P<0.03; means bearing different lower case letters differ significantly). This apparent decline in cyclin B1 transcripts over time appears to be indicative of maternal mRNA degradation. In addition, these results suggest that the porcine cyclin B1 MZTT did not occur over the majority of the 4-cell stage studied, or the transition was not detectable by our methods.

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